1. Field of the Invention.
The present invention relates generally to spraying equipment and in particular to a boom or wing height control system for an agricultural sprayer.
2. Description of the Relevant Art.
Agricultural fields are often sprayed with various chemical solutions, including fertilizers, herbicides, insecticides, etc. Various types of equipment are available for applying such chemical solutions. For example, aircraft are often used for field spraying and can cover relatively large areas at high speeds. However, more precise spraying can often be achieved with ground equipment, including pickup trucks fitted with spray equipment and systems. For example, a typical spray system might include: a tank mounted in a pickup truck bed; chemical mixing equipment; a pump; and a pair of booms or wings extending laterally from the vehicle and mounting the spray nozzles and associated tubing.
Spray systems have been devised with spray booms which extend laterally twenty feet or more from the vehicle sides. Operational efficiency advantages can be achieved with equipment capable of covering relatively wide swaths because the number of passes required to cover a given area can be minimized by maximizing the overall span of the spray booms. However, such wide-swath spray equipment may be too wide to transport over roads, and can also be too wide to conveniently store in existing structures with the booms extended. These problems have been addressed by providing mechanisms for folding the booms between their extended field positions and their folded transport positions. Transport positions for folding booms are often alongside the vehicles whereby the booms may swing through arcs of approximately ninety degrees between their field and transport positions.
Another problem with boom spraying equipment relates to difficulties in conforming the spray booms in their field positions to the terrain. These problems are exacerbated by sloping and uneven field conditions, and are further exacerbated by relatively wide-span spray booms which can create relatively large moment arms at the vehicles. For spray chemical coverage, the spray nozzles mounted on the booms should preferably be positioned at uniform heights above the field or crop surface. However, when traversing a sloping field, the boom on one side of the vehicle may need to be raised while the other boom may need to be lowered to maintain a relatively uniform spraying height for effective coverage. This problem has been addressed by providing boom elevation controls, which can be operated for each boom independently from the vehicle cab. However, manually controlled boom elevation systems are susceptible to human error factors in operation. For example, operators may have difficulty adjusting the elevations of a pair of spray booms in response to changing field contours while keeping the vehicle on a straight course.
Automatic height control devices have heretofore been utilized on agricultural equipment. For example, the Bettoncourt et al. U.S. Pat. No. 4,414,792 discloses a tomato harvester with a height control system utilizing ultrasonic signals for automatically determining an operating height of the machine. A hydraulic system is disclosed for adjusting the operating height in response to a control system which receives and processes the ultrasonic signals in the Bettoncourt et al. machine. The Thornelly et al. U.S. Pat. No. 4,507,910 discloses an automatic sonar activated height control for a combine header. The Siferling U.S. Pat. No. 4,573,124 discloses another height control for a tomato harvester which utilizes ultrasonic signals for determining operating heights.
Heretofore there has not been available a spraying system with an automatic height control with the advantages and features of the present invention.